With the resurgence in the specialty soap market, consumers are being offered personal washing bars that have a much more hand crafted “one-of a kind” appearance—so called artisan soaps. Technically such bars have several characteristics that contribute to their distinctive appearance: i) sharpness of the boundary between the phases; ii) easily recognizable difference in optical texture and/or pattern that goes beyond color; and iii) a certain degree of bar to bar non-uniformity. Differences in optical texture and pattern are especially important to convey a collection of sensory expectations associated with bar.
To achieve a highly distinctive appearances, artisan soaps have been predominantly made by cast melt processes—either single casting or sequential multiple casts. For example, U.S. Pat. No. US 2003/0171232—2003 to Freeman et al discloses a decorative soap that contains soap inclusions that are coated with a glitter agent (metallic pigment) in a powder coater. The coating makes the soap inclusions resemble a mineral.
Although melt-cast processes can yield bars with highly controlled patterns, they are generally slow and labor intensive. Consequently, multiphase artisan soaps are relatively expensive and tend to be confined to upscale specialty shops and outlets. Furthermore, melt cast soaps are known to have high wear rates and mushing characteristics that make them less preferred for everyday use.
The objective of the present invention is a multiphase bar that has an unusual artisan-crafted appearance yet can be produced by an efficient high speed extrusion process and conventional stamping.
A further objective is an artisan bar that have wear rate and mushing properties characteristic of milled soap and is thus economical for everyday use.
U.S. Pat. No. 6,730,642 to Aronson et al describes an extruded soap in which is dispersed a second phase that is added as solid pieces prior to the final compaction step in billet formation. By controlling the hardness ratio of the two solids, deformation of dispersed phase during extrusion can be minimized thus producing bars with visually distinctive chunks or bits dispersed throughout.
The present work targets an extruded multiphase bar having a very different structure in which the inclusion is in the form of a veins or ribbon located in the interior of the bar. This structure produces an appearance that is reminiscent of a translucent natural mineral such as for example, quartz or opal in which inclusions of a different composition are visible or become visible veins within the mineral. Technically, this appearance arises from the inclusion having a substantial surface area being approximately spatially confined within to a relatively thin volume slice in the material, i.e. ribbon-like structure. The inclusions are also optically non uniform. When the mineral is translucent or transparent the vein or ribbon can be perceived deep within the material while if the mineral is opaque the vein is only visible when present very close to the surface or when the mineral is fractured or ground to expose the vein.
Various attempts to approximate a veined appearance in bars have been described in the soap art under the heading of variegated, marbled, striated, and striped soaps. Prior art has mainly focused on routes to reproducibly achieve spatial variation in dye or pigment concentration as the primary means of generating bars that appear as comprising multiple phases.
One commonly used technique to make striated soaps is to combination of different color noodles to form a mixture in for example the vacuum chamber of an extruder. This mixture is then extruded to form a billet which is then stamped into a bar. This method is disclosed in the following parents:
U.S. Pat. No. 3,673,294 to Matthaei et al, teaches a process to form multicolored bars by extruding a mixture of two noodles which are required to have the same viscosity and essentially the same hardness (penetration value).
U.S. Pat. No. 3,940,220 to D'Arcangeli teaches the extrusion of a mixture of two noodles in which it is required that the discontinuous phase be softer [lower penetration value] than the main soap.
U.S. Pat. No. 3,993,722, to Borcher et al and U.S. Pat. No. 4,092,388 to Lewis teaches processes of combining different colored noodles to formed marbled soap. The two noodles have essentially the same composition apart from colorant and the two different color noodles have essentially the same temperature at the time of extrusion.
U.S. Pat. No. 4,310,479 to Ooms et al teaches a process for combining a minor amount of opaque noodles with transparent noodles to form a transparent marbled bar. The noodles should differ in water content by no more than 3% and are at the same temperature during extrusion.
U.S. Pat. No. 6,390,797 to Meyers teaches a process for making marbleized or speckled soap by addition of a second stream of colored soap pellets into the inner of the final stage plodder at a specific point.
A second common method of producing striated soaps is the injection of a dye solution during extrusion. Examples of patents disclosing this type of process include:
U.S. Pat. No. 4,474,545 to Mazzoni teaches radial dye injection at nose cone entry and employs a rotor within nose cone to produce wavy stripes.
U.S. Pat. No. 3,676,538 Patterson teaches the injection of a saponaceous dye solution through screw of plodder at the pressure plate before nosecone to make marbled soaps.
U.S. Pat. No. 3,663,671 to Meye et al teaches injection of dye solution into at least two inlets in the jacket of the plodder of an extruder in set locations.
U.S. Pat. No. 3,832,431 to Matthaei discloses injection of dye in given rates, at specific point through the wall in the barrel of the final stage extruder to make marbled bars.
U.S. Pat. No. 4,304,745 to Alderson et al discloses soap extruded via single screw through a perforated plate having large holes at the periphery and small holes in the center. Dye is injected in the middle of the plate to form bars with large colored striped at surface.
U.S. Pat. No. 4,720,365 to Shonig et al discloses the addition of liquid dye after pressured exit of final extruder via a pressure plate which has multiple holes to form finely striated bars.
In both of the broad methods described above (extrusion of a combination of colored noodles and dye injection) the multicolored soap mass undergoes considerable extensional and/or shear flow during billet formation. Consequently, the numerous multiple striations so produced are randomly located throughout the bar and are generally elongate structures that individually have relatively small width in comparison with the overall width of the bar.
Coextrusion has also been used to make striped soaps. For example:
U.S. Pat. No. 3,884,605 to Grelon teaches an apparatus for making striated soap by coextrusion where it is desirable that the two soaps have identical material properties, e.g., hardness, apart from color.
U.S. Pat. No. 6,383,999 to Coyle et al teaches a coextruded multiphase bar in which the phases differ in the level of emollient but must have similar flow properties under extrusion process conditions.
WO 01/91990 to Trinque discloses a “soap striater” comprising a primary and perpendicular plodder feeding a tube partitioned chamber exiting a perforated pressure plate into a nose cone. Some of the apertures may be blocked to get different patterns
U.S. Pat. No. 3,294,692 to Kelly et al discloses a striped bar made by injecting different colored masses into “grooved billet” through multiple extruders feeding a single chamber.
The coextruded bars described above have a pattern of distinctive multiple stripes which are uniformly distributed throughout the bar. Each stripe is visually uniform and occupies a relatively small cross sectional area relative to the overall area of the bar.
In contrast, the bars of the present invention have one or more inner veins. By inner vein we mean a ribbon-like, preferably non-uniform, structure that does not touch the surface of the bar when the bar is first produced, i.e., there is a layer of extruded soap between the vein and the surface of the bar. Furthermore, each vein is located approximately within a volumetric slice orientated in a horizontal plane between the top and bottom surfaces of the bar. By the term horizontal plane is meant a plane that is parallel to either a plane that is tangential to the bottom surface of the bar or to a plane that is tangential to the top surface of the bar. For most bars of commercial interest, these top and bottom tangential planes are essentially parallel.
Another distinguishing feature of the bars of the current invention is the expanse of the inner vein. In contrast to previous multi-phase extruded bars, the inner vein forms a contiguous mass (connected) that occupies a substantial portion of the area of the overall bar within the volumetric slice where it is predominantly located.
For example, if the outer extruded phase was transparent and the inner vein was opaque, then an individual vein when viewed through the bar in a direction perpendicular to the top face would be observed to occupy an area that is at least about 15% of the total cross sectional area of the bar (considered a substantial portion of the area), preferably at least 20%, more preferably at least 30% and most preferably greater than 50% of the total cross sectional area of the bar.
An alternative description of substantial expanse of the vein can be given in terms of a characteristic dimensions relative to the bar. One such characteristic dimension is the maximum width of the vein within a specified plane of the bar relative to the maximum width of the overall bar. Using again the above example of a transparent outer phase and an opaque vein, then the inner vein when viewed through the bar in a direction perpendicular to the top face would be observed to have a maximum width that is at least about 15% of the maximum width of the bar (considered a substantial fraction of the overall width of the bar), preferably at least 20%, preferably at least 25%, more preferably at least about 30% and most preferably greater than 50% of the maximum width of the bar. The term width is used here in its normal sense to designate the smaller orthogonal dimension of the bar in a plane perpendicular to the top face of the bar.
By the term “maximum width of the inner vein” is meant the width of the vein at its widest point. By the term “maximum width of the bar” is meant the width of the bar at its widest point.
Bars having these and additional characteristics and properties can be made by following the teachings of the present invention.